Clipless bicycle pedals are pedals in which the traditional toe clip, or cage, is replaced by a locking mechanism with which a cleat, fixed to the bottom of the rider's shoe, is engaged, allowing the rider to be securely connected to the pedal during pedal strokes, yet also allowing easy disengagement with a simple twist of the foot.
Clipless pedals should ideally be strong and durable, rebuildable for maintenance, light weight, and properly working even when the pedal and/or shoe is covered with mud and debris.
One of the best clipless pedals currently available, also known as “eggbeater” pedal, has four sides for cleat engagement.
In versions without a separate pedal body, the entire pedal is free to rotate to allow cleat engagement with any of the four sides.
In this kind of pedals, the locking mechanism is comprised of two loops, which are held perpendicular to each other by a coil spring: therefore, the two loops are spring loaded relative to each other.
In versions with a pedal body, the four-sided mechanism can rotate within the body, to allow clip engagement with any of the four sides: this allows easy engagement, regardless of the pedal position.
A pedal of this type is shown in FIGS. 1-4, while a cleat assembly suitable to engage with such pedal is shown in FIG. 35.
The pedal 10 includes a four-sided locking mechanism 12 for engagement with cleat assembly 400 (FIG. 34).
Locking mechanism 12 includes a sleeve 30 (see FIGS. 3,4), which is insertable along the axle 38 of the pedal 10.
The locking mechanism 12 further includes a coil spring 13, an outer loop 14 and an inner loop 15, all inserted along the sleeve 30.
The opposite legs 16,17 of the coil spring 13 respectively engage with the outer loop 14 and with the inner loop 15, and they hold loops 14,15 perpendicular to each other.
The inner side surface 18 of the coil spring 13 is supported by sleeve 30.
These pedals have become the benchmark in engagement/disengagement ease, ease of rebuilding, mud shedding function, and they are also extremely light weight.
However, these pedals have some disadvantages, as clarified below.
The coil spring of the pedal is inserted along a supporting sleeve, and a fixture is required to assemble the loop/spring mechanism, because the coil spring forces the sleeve to be off-center during assembly.
This is necessary for the coil spring to preload the loops into their mutual perpendicular position.
In production this is not a problem, but it is not possible for a consumer to completely rebuild the pedal without the fixture.
As the coil spring tightly contacts the sleeve, the coil spring causes gouging into the sleeve surface over time, and this means that a hard material such as steel must be used for the sleeve.
The problem with using steel is that it is very dense compared to other materials such as aluminum or plastic, and therefore this determines an increase in weight of the pedal, which might not be acceptable.
As the coil spring tightly contacts the sleeve, the latter must be allowed to rotate within the pedal body: consequently, the seals between the body and the sleeve must be of the dynamic kind.
Dynamic seals are more difficult to achieve compared to static seals, and they are more susceptible to leaking.
When the loop mechanism is assembled, the goal is, for the coil spring, to hold the loops as perpendicular to each other as possible.
However, it is difficult to manufacture a coil spring with precisely located leg ends; if the leg ends of the coil spring are not nearly perfectly located, a certain play occurs when there is some amount of rotational play between the loops.
If such play between the loops is too large, then the cleat engagement is compromised.
Another disadvantage is that, in this kind of pedals, there is currently no engagement force adjustment: in other words, there is no way for the rider to adjust how much force it takes to engage into, or out, of the pedal.